Digital VCR with trick play image control

ABSTRACT

A digital video cassette recorder operates by the selection of predetermined replay speeds and the allocation of specific locations within each track from which data may be reproduced. These specific track locations are utilized during recording to place advance television image data for reproduction during trick play operation. The trick play image data is also reproduced during normal playback but may not be utilized. The specific track locations are selected to facilitate trick play operation at a plurality of speeds in both forward and reverse directions. Since the advanced television signal comprises a plurality of predicted frames, transition from trick play to normal speed replay requires a control function which is responsive to the reproduction, at normal replay speed, of an inter frame coded frame. Various methods of reproduced image transition are used for selecting both to and from trick play reproduction.

This invention relates to the field of digital video recording, and inparticular to reproduction of an high definition video signal at anon-standard speed.

BACKGROUND OF THE INVENTION

A digital video cassette recorder employing a helical scanning formathas been proposed by a standardization committee. The proposed standardspecifies digital recording of either standard definition (SD)television signals, for example NTSC or PAL, and high definitiontelevision signals having an MPEG compatible structure, such as aproposed Grand Alliance signal. The SD recorder utilizes a compressedcomponent video signal format employing intra field/frame DCT withadaptive quantization and variable length coding. The SD track formatcomprises 10 μm tracks, azimuth recorded without guard bands, with 10 or12 tracks per NTSC or PAL frame respectively. The tape cassette employs1/4" wide tape with an evaporated metal recording medium. The SD digitalVCR or DVCR, is intended for consumer use and has sufficient datarecording capability to record either NTSC (PAL) signals, or an advancedtelevision signal.

An advanced television or ATV signal has been developed by the GrandAlliance (GA) consortium. A specification document titled Grand AllianceHDTV System Specification was published in the 1994 Proceeding of the48^(th) Annual Broadcast Engineering Conference Proceedings. The GAsignal employs an MPEG compatible coding method which utilizes anintra-frame coded picture, termed I frame, a forward predicted frame,termed a P frame and a bidirectionally predicted frame, termed a Bframe. These three types of frames occur in a group known as a GOP orGroup Of Pictures. The number of frames in a GOP is user definable butmay comprise, for example, 15 frames. Each GOP contains one I frame,which is abutted by B frames, which are then interleaved with P frames.

In an analog consumer VCR, "Trick Play" or TP features such as picturein forward or reverse shuttle, fast or slow motion, are readilyachievable, since each recorded track typically contains one field.Hence reproduction at speeds other than standard, result in thereproducing head, or heads, crossing multiple tracks, and recoveringrecognizable horizontal picture segments. The GOP of an ATV signal,employing I, P and B frames, may be recorded occupying multiple trackson tape, for example, 10 tracks per frame and 150 tracks per GOP. Simplystated, when a DVCR is operated at a non-standard reproduction speed,replay heads transduce sections or segments from multiple tracks.Unfortunately these track segments no longer represent sections fromdiscrete records of consecutive image fields. Instead, the segmentscontain data resulting mainly from predicted frames of the GOP. Duringplay speed operation, I frame data is recovered which permits thereconstruction of the predicted B and P frames. Clearly, during "TrickPlay" operation, the amount of I frame data recovered progressivelydiminishes as TP speed increases. Hence, the possibility ofreconstructing B and P frames from the reproduced pieces of I frame datais virtually zero. Thus, the provision of "Trick Play" or non-standardspeed replay features requires that specific data be recorded, whichwhen reproduced in a TP mode, is capable of image reconstruction withoutthe use of adjacent frame information. Furthermore, since "Trick Play"specific data is recorded, the physical track location must be such topermit recovery in a TP mode.

SUMMARY OF THE INVENTION

In accordance with an inventive arrangement a digital video recorder forreproducing digital image signals at different reproducing speeds, saidrecorder comprises: a transducer for recovering a digital signal from arecorded medium, the digital signal having a first data signalrepresenting the digital image signals and a second data signalrepresenting a processed form of the digital image signals; meanscoupled to the transducer for separating the digital signal into thefirst and the second data signals; means responsive to a selection ofone of the selected reproducing speeds and at least one of the first andsecond data signals for generating an image source control signal; and,selecting means coupled to the separating means and responsive to thecontrol signal for selecting between the first and second data signalsas output image sources.

In accordance with another inventive arrangement a digital videorecorder employing a helical scanning format for reproducing a digitalimage signal, the recorder comprises: a play back transducer fortransducing a digital signal from a recorded medium, the digital signalhaving a first data signal, having a compatible MPEG format andrepresenting the digital image signal and a second data signal having acompatible MPEG format and representing a processed form of the digitalimage signal; means coupled to the transducer for separating the digitalsignal into the first and the second data signals; selecting meanscoupled to the separating means and responsive to a control signal forselecting the second data signal at initiation of reproduction andselecting the first data signal following reproduction of an I frameidentifying signal from the first data signal; and, decoding meanscoupled to an output of the selecting means for generating the digitalimage signal from the first and the second data signals.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 illustrates a recorded track pattern showing the locations ofvarious data sectors as specified for a standard definition DVCR.

FIG. 2 illustrates the replay head path with areas of sync blockrecovery at twice replay speed.

FIG. 3 illustrates the replay head path with areas of sync blockrecovery at four times replay speed.

FIG. 4 illustrates the replay head path with areas of sync blockrecovery at eight times replay speed.

FIG. 5 illustrates the replay head path with areas of sync blockrecovery at sixteen times replay speed.

FIGS. 6A-6B contain tables showing audio and video sync-blocks recoveredat various trick mode replay speeds.

FIG. 7A illustrates sync-blocks recovered at 2, 4, 8 and 16 times replayspeeds.

FIG. 7B illustrates recovered sync-blocks common to 2, 4, 8 and 16 timesreplay speeds.

FIG. 8 illustrates a first embodiment of a recorded track patternshowing advantageous sync block locations for placement of inventive"Trick Play" data.

FIG. 9 illustrates the replay head path and track areas of sync blockrecovery at 3 times play speed.

FIG. 10 illustrates the replay head path and track areas of sync blockrecovery at 9 times play speed.

FIG. 11 illustrates the replay head path and track areas of sync blockrecovery at 19 times play speed.

FIG. 12 illustrates the replay head path and track areas of sync blockrecovery at minus 1 times play speed.

FIG. 13 illustrates the replay head path and track areas of sync blockrecovery at minus 7 times play speed.

FIG. 14 illustrates the replay head path and track areas of sync blockrecovery at minus 17 times play speed.

FIG. 15 illustrates sync-blocks recovered at 3, 9 and 19 times forwardplay speeds and 1, 7 and 17 times play speed in the reverse direction.

FIG. 16 illustrates a second embodiment of a recorded track patternshowing inventive sync block locations for recording inventive "TrickPlay" data.

FIG. 17 illustrates a video data sector recorded with an ATV signal andan inventive "Trick Play" signal.

FIG. 18A illustrates the arrangement of data within a SD sync block.

FIG. 18B illustrates a sync block advantageously formatted for recordingboth ATV and inventive "Trick Play" data signals.

FIG. 19 is a system block diagram of an ATV digital video cassetterecorder employing an inventive "Trick Play" recording and replayfeatures.

FIG. 20 is a system block diagram of an inventive "Trick Play" encoderand decoder.

FIG. 21 is a system block diagram showing an SD recorder and inventivecontrol of "Trick Play" and high definition video playback.

DETAILED DESCRIPTION

FIG. 1 shows a recorded track format for a consumer use, standarddefinition (SD), helical scan, digital video cassette recorder. Theeffective data area shown in FIG. 1 comprises four sectors in whichspecific types of data are recorded. The ITI, or Insert and TrackInformation data sector is used for tracking and editing, and isfollowed by an editing gap G1. An audio data sector occupies 14 syncblocks, numbered 0-13. A second editing gap G2, follows the audio datasector, which is followed by a video data sector comprising 149 syncblocks, numbered 0-148. A third editing gap G3 follows the video datasector which is in turn followed by a sub code recording sector. Thedigital video cassette recorder or DVCR, is specified to have a digitalvideo recording rate of 24.948 Mbps. This video bit rate may be utilizedfor recording a component video signal decoded from either an NTSC (PAL)signal, or a processed advanced television signal, such as for example,the GA signal. FIG. 21 shows, a simplified block diagram of a DVCR 350.DVCR 350 comprises a head drum 510 which includes a plurality ofrecording and reproducing heads which are coupled to a playbackprocessor that generates four output signals, 351, 352, 353 and 354.Replay signal 354 represents an ATV data stream and the data processingpath is depicted by blocks 359, 120 and 130. "Trick Play" image data isrepresented by replay signal 353 which is shown coupled to subsequent"Trick Play" image data processing. The processing and selection between"Trick Play" and ATV images will be described later. A cassette 501, isshown inserted into DVCR 350, with tape 504 threaded around the headdrum 510.

The SD track format may be recorded with various head placements on thedrum or cylinder, and with various drum rotational speeds. The trackpatterns which follow illustrate replay head paths or tracks for various"Trick Play" speeds. In addition, two possible head drum configurationsare illustrated, i.e. a double azimuth head pair, and two single heads180° diametrically opposed on the drum.

FIGS. 2-5 illustrate replay head paths for a selection of "Trick Play"reproduction speeds. The tape is recorded according to the SD, digitalvideo cassette recorder format, with 10 μm tracks, azimuth recordedwithout guard bands, and is illustrated replayed by a replay head withpole face width of 15 μm.

FIG. 2 illustrates the replay head path or footprint, at twice speedreproduction. The footprint shown is for a single pair of double azimuthreplay heads. It is assumed that the replay head will recover sync blockdata from the recorded track until half the recorded track width isscanned. The FIGURES depict track areas of sync block data recovery bycross hatching.

FIGS. 3, 4 and 5 illustrates the replay footprints at four, eight andsixteen times play speed respectively.

FIG. 6A is a table showing track numbers and the numbered sync blocksrecovered from the audio data sector at the TP speeds illustrated inFIGS. 2-5. FIG. 6B shows the tracks, and numbered sync blocks, recoveredfrom the video data sector at the Trick Play speeds illustrated.

The recovered video sync block data depicted by cross hatching in FIGS.2, 3, 4 and 5, and the numbered sync blocks, of table FIG. 6B, arecombined and illustrated in FIG. 7A for

TP speeds of 2, 4, 8 and 16 times. FIG. 7B illustrates track areas andnumbered sync blocks recovered, which are common to all four speeds.Thus FIG. 7B indicates track locations, identified by sync block number,where data may be recorded and recovered at play speed and at 2, 4, 8and 16 times play speed.

FIG. 8 shows one recorded track comprising an ITI, or Insert and TrackInformation recording area, editing gap G1, an audio data recording areaoccupying 14 sync blocks, numbers 0-13. During ATV operation audio andvideo data are conveyed within the ATV data transport stream thus theaudio data sector is not required for audio data use and may be utilizedfor ATV and "Trick Play" data recording. A second editing gap G2,follows the audio data sector and it is followed by a video datarecording sector comprising 149 sync blocks, numbered 1-149. A thirdediting gap G3 follows the video data sector which is in turn followedby a sub code recording area. The recorded track of FIG. 8 shows anadvantageous first embodiment of sync block allocation for inventive TPdata recording, where 5 sync blocks are used in the audio sector, and 40sync blocks are utilized in the video sector. Thus 45 sync blocks may beutilized in each scan to record TP video data for recovery at bothstandard and nonstandard play speeds. These 45 TP sync blocks provide aneffective replay data rate of about 1.06 Mbit/sec at nominal speed.

FIGS. 9-11 illustrate replay head paths for "Trick Play" speeds of 3times, 9 times and 19 times, with head footprints for both doubleazimuth and 180° diametrically opposed heads.

FIG. 9 illustrates track areas of sync block recovery at 3 times playspeed. Tracks T1 and T2 represent reproduction with double azimuth headpair, tracks T1 and T4 represent reproduction by 180° opposed heads.FIG. 9 shows that for either type of replay head configuration there areareas of the track, and consequently sync blocks, which are neverrecovered.

FIG. 10 illustrates track areas of sync block recovery at 9 times playspeed. Tracks T1 and T2 represent reproduction with double azimuth headpair, tracks T1 and T10 represent reproduction by 180° opposed heads.

FIG. 11 illustrates track areas of sync block recovery at 19 times playspeed. Tracks T1 and T2 represent reproduction with double azimuth headpair, tracks T1 and T20 represent reproduction by 180° opposed heads.

FIG. 12 illustrates track areas of sync block recovery at minus 1 timesplay speed. Tracks T3 and T4 represent reproduction with double azimuthhead pair, tracks T3 and T2 represent reproduction by 180° opposedheads.

FIG. 13 illustrates track areas of sync block recovery at minus 7 timesplay speed. Tracks T17 and T18 represent reproduction with doubleazimuth head pair, tracks T17 and T10 represent reproduction by 180°opposed heads.

FIG. 14 illustrates track areas of sync block recovery at minus 17 timesplay speed. Tracks T21 and T22 represent reproduction with doubleazimuth head pair, tracks T21 and T4 represent reproduction by 180°opposed heads.

The sync blocks recovered at the various forward and reverse speedsshown in FIGS. 9-14, are combined and illustrated as single tracks. FIG.15A, illustrates numbered sync blocks at 3 times speed, FIG. 15B, showsSBs recovered at 9 times speed, FIG. 15C, for 19 times speed, FIG. 15D,for minus 1 times speed, FIG. 15E, for minus 7 times speed, and FIG.15F, for minus 17 times speed. FIG. 15G represents analysis of therecovered sync blocks for commonalty. Thus FIG. 15G shows numbered syncblocks which are recovered at 3, 9 and 19 times in the forward directionand 1, 7 and 19 in reverse directions.

FIG. 16 illustrates a second embodiment having advantageous tracklocations, identified by sync block number, where 45 sync blocks ofinventive "Trick play" video data may be recorded and recovered at playspeed and at play speeds of 3, 9 and 19 times in the forward directionand 1, 7 and 17 times in the reverse direction.

An ATV bit stream may be recorded in the data capacity of 105 syncblocks, which are composed of 14 sync blocks from the audio data sectorand 91 SB from the video data sector. The inventive "Trick Play" videodata may be recorded using 45 SB within the video data sector. In FIG.17, a video data sector is illustrated showing sync block (SB) structurefor an ATV data recording.

FIGS. 18 A and B illustrate the data structure of a sync block, SB,within the video data sector. FIG. 18A illustrates a standard definitionor SD formatted sync block. The SD sync block comprises 90 bytes, with77 bytes containing 6 groups of discrete cosine transformed or DCTcoefficient data. Each DCT group comprises a DC coefficient valuefollowed by AC coefficient values in descending order of significance.FIG. 18B illustrates a sync block formatted with inventive "Trick Play"data. "Trick Play" data is compressed, discrete cosine transformed andvariable length coded, as will be described for FIG. 20. Two compressedTP macro blocks may be recorded in one sync block, formatted as shown inFIG. 18B.

Having identified sync block locations advantageous to "Trick Play"reproduction in both forward and reverse directions at various speeds,"Trick Play" video data must be derived from the ATV data stream. Asdescribed earlier, TP sync blocks recovered during "Trick Play" modereplay, must be capable of decoding to produce images without referenceto, or prediction from, adjacent image frames. Clearly "Trick Play"video data may be derived from intraframe or I frame coded video.However, derivation of "Trick Play" video exclusively from I frames may,as a consequence of the low repetition rate of I frames within each GOP,result in stroboscopic or jerky rendition of motion in "Trick Play"modes. Thus, to avoid jerky "Trick Play" motion, video for "Trick

Play" record processing is advantageously derived from video, decodedfrom the ATV or MPEG like data stream. Hence every decoded picture,derived from I, P or B frames, is processed to generate corresponding"Trick Play" frames for recording. Thus each recorded frame in a GOPcontains a corresponding "Trick Play" processed image which, during"Trick Play" reproduction, may be decoded to provide images in whichmotion is smoothly portrayed.

The DVCR format allocates ten recorded tracks to one ATV frame, thus thesame number of recorded tracks is selected for the "Trick Play" videodata. The ATV data may be allocated 105 SB per track, thus a recordedATV frame corresponds to 1050 SBs. Since "Trick Play" video data may beallocated 45 sync blocks per video sector, a total of 450 SBs areutilizable for "Trick Play" data recording. Hence each "Trick Play"video frame must be compressed to occupy the data capacity provided bythe 450 sync blocks. The required degree of the "Trick Play" video datacompression may be represented by 450:1050 or approximately 2.3 to 1.

FIG. 19 is a block diagram of an advanced television receiver employingan inventive method of Trick Play mode processing for recording an MPEGlike data stream on a standard definition or SD, digital video cassetterecorder. The block diagram comprises an ATV decoder 100, a Trick Playprocessor 200, and an SD DVCR 300. An exemplary RF modulated advancedtelevision signal is received by an antenna 101, and is coupled to aninput of an ATV decoder 100. The RF modulated signal may also bedelivered to decoder 100 via a cable distribution system. Decoder 100comprises a channel demodulator 110, which extracts the modulated, MPEGlike, ATV bit stream signal from the RF carrier. The bit stream has adata rate of 19.3 Mbs, and is coupled as output signals 111 and 112. Bitstream 111 is coupled to a transport packetization decoder 120, which insimple terms, separates video data packets 121, from audio data packets122. The video data packets 121 are coupled to a video compressiondecoder 130 which reconstructs HD video image signals. The video signals131, are coupled to a video processor and sync generator 150, whichgenerates at output 151, the original 16:9 aspect ratio high definitionvideo signals, for example, luminance and color difference signals Crand Cb. The video processor and sync generator 150, also receives asecond input signal 132 from pixel converter 280, of the Trick Playprocessor 200. The audio data packets 122 are coupled to an audiocompression decoder 140 which extracts and regenerates the originalaudio signals which form audio output signals 141.

The MPEG like bit stream signal 112, is coupled to a bit stream rateconverter 310, which converts the 19.3 Mbs bit stream to a data rate of24.945 Mbs, as required for processing and recording by the SD recorder.The output from rate converter 310 is coupled to an inner and outerparity generator 320 which generates Reed Solomon error correction codeswhich are included in the video data recorded in the video sector, asdepicted in FIG. 1. Following the insertion of RS error correction codesthe data stream is coupled to an SD video data sync block structurer330, which constructs video data-sync block structure required by the SDrecorder format.

Block 340 of FIG. 19, constructs audio and video sectors according tothe SD format, where video data sector includes processed ATV data fromblock 330, plus inventive "Trick Play" video data 251, from block 250 of"Trick Play" video processor 200.

The SD video sector format or structure, is illustrated in FIGS. 17, 18Aand 18B. FIGS. 18A and 18B show the sector comprises a video preamble,149 sync blocks of video data and error correction code, and a videopost-amble. The sync blocks are numbered 1 through 149. FIG. 18A depictsan SD format employed during the recording of an NTSC image source. FIG.18B shows ATV video data advantageously recorded occupying, for example,105 sync blocks. Inventive "Trick Play" video data may be recordedoccupying, for example, 45 sync blocks and video auxiliary data may berecorded with 2 sync blocks. Outer parity error correction data isrecorded using 11 sync blocks.

The ATV video sector data, including "Trick Play" data and audio sectorsignals are coupled from block 340 to a standard definition or SDdigital video cassette recorder 350. The SD recorder may also receive ananalog NTSC (PAL) input signal for recording. The analog signal isdecoded into luminance and color difference components and, for NTSCinput signals, the components are 4:1:1 sampled at 13.5 MHz anddigitized to 8 bits. The digitized NTSC signal is compressed accordingto the SD recording format which employs intra-field/frame DCT appliedto 8×8 image blocks, followed by adaptive quantization and modified twodimensional Huffman encoding. The image blocks are shuffled, orredistributed, throughout each frame to prevent recording media damageproducing uncorrectable data errors. Since the image blocks are shuffledprior to recording, any large media related reproduction errors will bedistributed throughout the decoded frame as a result of complementarydeshuffling employed during reproduction. Thus large potentiallyuncorrectable, and therefor visible errors, are distributed and may becorrectable by the inner and outer Reed Solomon error correction codes.Following compression, the data is coded for recording using a 24:25transformation which allows frequency response shaping to provide autotracking capabilities on replay.

The SD recorder 350 reproduces four output signals, 351, 352, 353 and354. Output signals, 351 and 352 are base band analog signalscomprising, video components Y, Cr and Cb, and audio signalsrespectively. Signal 351 comprises video components which are coupled toan NTSC sync generator and encoder 360, which provides blanking and syncpulse addition for video monitor viewing. The components may be encodedto produce an NTSC signal for viewing on a standard definition TVreceiver.

SD recorder 350 generates an ATV data bit stream output signal 354, anda "Trick Play" data bit stream output signal 353. Signal 353 is coupledvia error correcting block 259 to block 260 of the ATV and "Trick Play"processor 200 for decompression and subsequent up conversion to an ATVsignal format. The operation of "Trick Play" processor 200 will bedescribed with reference to FIG. 20.

Data bit stream 354, is coupled via error correcting block 359 to block120 of ATV decoder 100, where the replayed transport packets aredecoded. A decoded ATV signal 131, is coupled from the video compressiondecoder 130, to line rate converter 210, of the ATV and "Trick Play"processor 200. The ATV signal comprises luminance and color differencesignals, Cr and Cb, and may for example, comprise 1080 active horizontalscan lines each having 1920 pixels or samples. Line rate converter 210,reduces the number of active scan lines to one third, or 360 lines. Thusthe luminance and color difference signals which are processed to form a"Trick Play" video signal having one third of the vertical resolution ofthe original ATV signal. The line number conversion is performed by avertical low pass filter function. The line rate reduced signal fromconverter 210 is coupled to a pixel converter 220 which reduces thenumber of pixels to one third by low pass filtering. Thus, signal 221comprises 360 horizontal lines each containing 640 pixels, and ATVsignal 131, has been transformed, or down converted, into a signalhaving "NTSC" like parameters. Since the ATV signal had an aspect ratioof 16:9, so to will signal 131. However, the down converted signal 221will display the 16:9 image in a letter box format.

The down converted signal 221 is also coupled to NTSC encoder 360 forsync and blanking addition and encoding for standard definition viewingon a receiver or video monitor. Signal 221 is also coupled to a signalcompression processor represented by block 230, the details of whichwill be described with respect to FIG. 20. However, in simple terms, thepurpose of signal compression processor 230 is to generate a compressedform of the down converted ATV signal. For example, signal compressionprocessor 230, may compress signal 221 by approximately 2.3 times.

The compressed, down converted signal is utilized to provide "TrickPlay" video data for recording at specific sync blocks within eachtrack, for example, as shown in FIGS. 8 and 16. Data for each TP videoframe is recorded within the ten tracks which comprise each ATV SDrecorded frame. Thus TP video data may be considered to be redundantlyrecorded within the video data sectors of the tracks comprising an ATVSD frame. During normal speed playback, TP video data is reproducedtogether with the ATV data but may not be used in the formation of anATV image. However, since a "Trick Play" data frame occurs in every tenrecorded tracks, these TP frames may be recovered during normal playbackand stored to be utilized during a replay mode transition. For example,a transition from normal speed forward playback to high speed "TrickPlay" or picture in shuttle. In a worst case situation, when a normalspeed replay is initiated, approximately 140 recorded tracks may bereproduced before an I frame is recovered. However, since TP data framesare advantageously recorded throughout each GOP, "Trick Play" processedimages may be produced immediately following the reproduction of anyframe type. Thus a "Trick Play" processed image may be available to beoutput during the initiation of a normal speed replay prior to recoveryand decoding of a NP I frame. Upon I frame acquisition the output may beswitched from "Trick Play" to ATV images.

The compressed TP signal from block 230 is coupled to an inner paritygenerator 240, which adds Reed Soloman error correcting data to the TPdata stream. The TP video data, with RS inner parity added, is coupledto a TP video data sync block formatter 250, which generates only thespecific numbered sync blocks required for "Trick Play" reproduction atspecific speeds. For example, "Trick Play" reproduction at variousspeeds is possible with sync blocks allocated as shown in theembodiments of FIGS. 8 or 16. These TP video data sync blocks are outputas signal 251 which is coupled to the video and audio sector constructor340 of SD DVCR 300.

During playback SD recorder 350 reproduces "Trick Play" data signal 353,which coupled to an error correcting processor 259. Following errorcorrection the TP data stream is coupled for signal decompression inprocessing block 260 of the ATV and "Trick Play" processor 200. Thedetails operation of block 260 will be described with respect to FIG.20. However, in simple terms, decompressor 260 is utilized to regeneratedown converted ATV images from the compressed TP data recovered from therecording medium.

An inventive "Trick Play" signal compression processor, for generatingdata signal 251, is shown in blocks 234-238 of FIG. 20. Replayed TP datamay be decompressed by blocks 262-266 of FIG. 20. Rate reduced ATVsignal 221, is coupled to formatter 234, which converts the scan lineformat of signal 221 into a two dimensional macro block or MB, structurecomprising 4 DCT blocks. Thus a macro block has the dimensions of 32pixels by 8 lines. The macro block formatted, rate reduced signal, iscoupled to block 235 for discrete cosine transformation. The principalsof the discrete cosine transform are well known, with a data ratereduction ensuing from the control of coefficient quantization. DCTblock 235, produces two output signals which represent the amplitudevalue of the frequency coefficients that comprise each macro block. Oneoutput signal is coupled to block 236 which pre-analyzes the amplitudesof the coefficients and controls the coarseness or fineness ofquantization by quantizer block 237. The second output from DCT block235 is coupled to quantizer block 237 for quantization, where the numberof quantizing steps is dynamically controlled responsive to block 236.The quantized DCT coefficients are coupled to block 238 for variablelength encoding. Various methods of variable length coding or VLC areknown. However, in simplistic terms, the most frequently occurringquantized coefficient values are assigned correspondingly short codewords with less frequent coefficient values being encoded with codewords of progressively increasing length. Thus the overall data rate ofTP video data is further reduced such that a "Trick Play" frame of datamay be recorded in 450 sync blocks provided in 10 recorded tracks.

The variably length coded TP data is coupled to block 240 for generationand addition of a Reed-Soloman inner parity error correction code. TheTP data with RS inner parity error correction is coupled to block 250for formatting to have a specific SD sync block structure, for example,as identified in FIGS. 8 and 16. The TP data having the required syncblock structure is coupled to the SD recorder as already described for"Trick Play" processor block 200.

During replay modes, the reproduced TP data stream signal 353, iscoupled via error correction in block 259, to decompression block 260which reverses the signal processing performed by block 230. The VLC TPdata signal 353 is input to block 266 which performs variable lengthdecoding. Various methods of decoding are well known, for example, alook up table could be used to convert VLC data words back intoquantized DCT coefficients of constant length. From block 266 the TP DCTcoefficients are coupled to an inverse quantizer 262, which may beconsidered to perform digital to analog conversion of the TP DCTcoefficients. The TP DCT coefficients are coupled to block 263 whichapplies an inverse discrete cosine transformation which produces a macroblock formatted output signal representing the TP image. The macro blocksampled TP signal is reformatted in block 264 to produce a conventionalline structured image. The output signal from the reformatter 264 isprocessed in block 265 which, for example, may provide blankinginsertion and sync pulse addition. Signal 261 is output from block 265and may be coupled for viewing on a component video monitor, or may beencoded for TV viewing. A second output signal 271, from block 264 iscoupled to blocks 270 and 280 which provide up conversion from thenominally "NTSC" like line and pixel formats to line rates andhorizontal pixel counts required for high definition display viewing.

The up converted TP video signal 131 is coupled as a second input tovideo processor and sync generator 150, which generates a highdefinition output signal 151. Video processor and sync generator 150provides video blanking and the addition of HDTV sync waveforms.However, in addition video processor 150 provides a selecting functionfor switching between ATV and "Trick Play" video images. FIG. 21 shows,in block diagram form, the replay data paths for ATV data stream 354 and"Trick Play" data stream 353, and their coupling for output selection invideo processor and sync generator 150. The selection of output imagesource is ultimately responsive to user initiated control commandcommunicated via a control system. For example, a Play command willstart the VCR mechanism and switch the electronic system from an EEmode, (electronics to electronics) to a replay condition. However, theactual instant of output signal switching may be determined by variousother controlling factors. For example, the most significant controllingevent may be the acquisition and decoding of an I frame from a recordedGOP. This occurrence may be signaled by decoder 130 and coupled tocontrol the video output selector switch within the video processor andsync generator 150.

As described earlier, a 15 frame GOP will occupy 150 recorded tracks,thus when initiating play mode, a replayed video image may be delayeduntil an I frame has been reproduced and decoded, i.e. up to 140 tracksmay need to be reproduced until an I frame is encountered. However,since TP data is advantageously recorded within each frame of a GOP, andis reproduced in a normal play mode, TP data may be utilized to generatean output video signal without waiting for an I frame occurrence. Thusthe redundant nature of TP data recording may advantageously provideimages for normal speed replay, derived from TP data, at the initiationof normal playback, with ATV images being selected when available,following I frame acquisition.

When a user initiates a command starting or terminating a "Trick Play"mode, the control system, and in particular the video processor and syncgenerator 150, may be advantageously controlled to present the user witha more aesthetically pleasing image transition. For example, as alreadydescribed, at the initiation of normal speed playback "Trick Play"images may be output, prior to the acquisition and decoding of an Iframe. A further use of TP video data may be during the transition to a"Trick Play" reproducing speed, where TP video data which was recoveredand stored during normal playback may used together with TP datatransduced during a replay speed transition. Such a use of TP dataprovides an alternative to sustaining the last ATV frame until TP videodata is available at the selected TP speed.

When transitioning from a "Trick Play" mode to normal play, the ATVsignal 131 will become available for display processing only after theoccurrence an I frame in the replayed ATV signal GOP. This I frameoccurrence depends on the resynchronization rate of the SD recordercapstan servo, and more significantly, where in the recorded GOPsequence normal play speed was re-acquired. Thus various options may beadvantageously provided to produce a pleasing image transition between"Trick Play" and normal playback. For example, upon the commandterminating "Trick Play" the last TP frame may be frozen and repeatedfrom a memory until ATV signals are reproduced. This method may indicateto the user that the control command has been received and executed.However, a frozen or still image juxtaposed with the fast moving imagesproduced in TP, may appear incongruous to the user. A further option fortransition from "Trick Play" may be provided by continuing to reproduceTP data and display TP images for the duration of servoresynchronization and ATV signal I frame acquisition. With this option,the redundant nature of the TP data may be exploited during the tapespeed change, resulting from the servo resynchronization, and during thewait for an ATV I frame. During the tape speed change, despite theredundant nature of the TP data, some TP data may not be recovered,however such errors may be concealed by TP image frames repeated from amemory. This advantageous method provides the user with a visualindication that the VCR is responding to the command since the speed ofthe TP image will visibly change as the capstan slows to re-synchronizeat play speed. This feature may also permit slower tape speedtransitions to be used thus providing smoother and less potentiallydamaging tape handling since tape acceleration or deceleration will beaccompanied by accelerating or decelerating "Trick Play" images.

I claim:
 1. A digital video recorder for reproducing a digital imagesignal at a plurality of reproducing speeds, said recorder comprising:atransducer for recovering a digital signal from a recorded medium, saiddigital signal having a first data signal representing said digitalimage signal and a second data signal representing a form of saiddigital image signal processed for trick play reproduction; meanscoupled to said transducer for separating said digital signal into saidfirst and said second data signals; means responsive to a selection ofone of a plurality of reproducing speeds and at least one of said firstand second data signals for generating an image source control signal;and, selecting means coupled to said separating means and responsive tosaid control signal for selecting between said first and second datasignals for coupling to form output image sources; wherein during atransition from a non-reproducing mode to a normal play speedreproducing mode, said second data signal is selected for coupling toform an output image source until normal play speed is achievedwhereupon said first data signal is selected for coupling to form anoutput image source.
 2. The digital video recorder of claim 1, whereinsaid plurality reproducing speeds represent a first speed equal to anormal play speed and a second speed different from said normal playspeed.
 3. The digital video recorder of claim 2, wherein said first datasignal is selected as an output image source for reproduction at saidfirst speed.
 4. The digital video recorder of claim 2, wherein saidsecond data signal is selected as an output image source forreproduction at said second speed.
 5. The digital video recorder ofclaim 2, wherein during operation at said first speed said second speedis selected and said selecting means immediately selects said seconddata signal as an output image source.
 6. The digital video recorder ofclaim 2, wherein said second data signal is selected during a transitionfrom operation at said second speed to operation at said first speed andupon assumption of said first speed said first data signal is selected.7. The digital video recorder of claim 2, wherein a transition from anon-reproducing mode to said first speed said control signal controlssaid selecting means to select said second data signal for forming astill image and selecting said first data signal upon assumption of saidfirst speed.
 8. The digital video recorder of claim 1, wherein saiddigital image signals have an MPEG compatible format.
 9. The digitalvideo recorder of claim 1, wherein said plurality reproducing speedsrepresent a first speed equal to a normal play speed and a second speedequal to a normal play speed in a reverse direction to said first speed.10. The digital video recorder of claim 9, wherein said second datasignal is selected as an output image source for reproduction at saidsecond speed in said reverse direction.
 11. The digital video recorderof claim 1, wherein said processed form of said digital image signalsrepresents said digital image having reduced resolution.
 12. A digitalvideo recorder for reproducing a digital image signal, said recordercomprising:a play back transducer for transducing a digital signal froma recorded medium, said digital signal having first and second datasignals, having a compatible MPEG format and said first data signalrepresenting image data for reproduction at normal play speed and saidsecond data signal representing image data for reproduction at a speedgreater than normal play speeds; means coupled to said transducer forseparating said digital signal into said first and said second datasignals; selecting means coupled to said separating means for selectingone of said first and said second data signals; and, decoding meanscoupled to receive said one of said first and said second data signalsfor decoding to form a signal for display, wherein upon initiation ofreproduction said selecting means selects said second data signal forcoupling to said decoder, and responsive to said separating meansdetecting an I frame signal occurrence in said first data signal, saidselecting means selects said first data signal for coupling to saiddecoder.
 13. The digital video recorder of claim 12, wherein atransition from reproduction at a speed greater than normal play speedto reproduction reproduction at normal play speed said second datasignal is coupled for decoding and responsive to an I frame signaloccurrence in said first data signal said selecting means selects saidfirst data signal for coupling to said decoder.